Semi- synthetic vs. full synthetic

The recommended OCI is 10k but since dealer used semi-synthetic oil for the ToyotaCare free service, what’s the difference between these two? If full synthetic is better should we use 5k for semi- and 10k for full? Is the Mobil 1 ow-20 semi or full synthetic? Two service advisors gave me different answers. One said I should use 5k for semi and the other one says both are good for 10k.

 

Mobil 1 0w-20 is full synthetic (group 4 & 5 blends). Most full synthetic oils are mixtures of groups 3, 4 and 5 in their base stocks. However Mobil 1 has a long great track record.

 

Sounds like the dealer "cheaped out" on your free oil change. Exactly why I pass on that offer and do them myself.

 

If the oil the dealer puts in specified oil, then it meets the requirements for the Toyota recommended OCI. (If this OCI is adequate is another discussion). Plenty of Toyota’s running full 10 k ocis on dealer bulk though.

Mobil 1 0w20 does use grp III in the formulation however It doesn’t make much of a difference in the quality of the formulated product. The specifications carried are no different/better than Amazon basics or Walmart super tech of the same grade.

There are different factors to consider. Such as overall fuel mileage during the entire OCI to estimate a good OCI confirmed with oil analysis with a particle count and using gas chrmotaograph to accurately determine fuel dilution. It cost more to do right, And the value gained over a 5 k OCI is a loss.

 

"Two service advisors gave me different answers" -

https://autoweek.com/article/car-news/toyota-owners-spar-over-engine-sludge-problem

"Toyota understands that customers can sometimes be confused about how to properly maintain their vehicles. We're confident that this program will remind customers of their responsibility as well as reassure those who have had regular oil changes that they have nothing to be concerned about."

TOYOTA - Owners manual Section 9-1. Specifications page 571

Engine oil selection

“Toyota Genuine Motor Oil” is used in your Toyota vehicle. Use Toyota
approved “Toyota Genuine Motor Oil” or equivalent to satisfy
the following grade and viscosity.

Oil grade: ILSAC GF-5 multigrade engine oil
Recommended viscosity: SAE 0W-20

SAE 0W-20 is the best choice
for good fuel economy and
good starting in cold weather.

If SAE 0W-20 is not available,
SAE 5W-20 oil may be used.
However, it must be replaced
with SAE 0W-20 at the next oil
change.

Hope that helps
Cheers!

 

Hmmm, my dealer uses Mobil 1 on all their oil changes, even ToyotaCare.

 

This is the coupon from the dealership. My free maintenance expired. If the semi- synthetic last less than full then I’m planning to do oil change with full synthetic myself.

 

That's pricey!

 

Tire rotation included. Probably $40 if they charge separately.